Integrated photonic devices have great potential for a switching fabric in ultra-small photonic lightwave circuits (PLCs) on low-cost silicon-on-insulator (SOI) substrates. They can include waveguides, splitters, combiners, Mach-Zehnder interferometers, array waveguide gratings (AWGs), and photodiodes for processing optical signals, which fall within the customary telecommunication wavelength bands such as the 1310 nanometer (nm) or 1550 nm bands.
The fabrication process for PLCs is subject to dimensional and compositional tolerances, which may require active tuning or trimming elements in order to function as designed. Photodiodes may be used to monitor the state of the integrated photonic devices by providing electrical feedback signals to electronic driver circuitry used to control them.
As the PLC complexity increases with a growing number of integrated photonic devices, the number of required monitor photodiodes (MPDs) also increases. However, the number of available electrical connections to the PLC may be limited, which could severely limit the PLC complexity if each MPD were required to have an individual connection to external driver circuitry.